How many bytes does IP-IP tunneling add to an IP packet?
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A. B. C. D.A
Tunneling increases overhead, because it needs an extra set of IP headers. Typically this is 20 bytes per packet, so if the normal packet size (MTU) on a network is 1500 bytes, a packet that is sent through a tunnel can only be 1480 bytes big.
http://cs.uccs.edu/~scold/iptunnel.htmIP-IP tunneling is a technique used to encapsulate an IP packet within another IP packet. This technique is commonly used in VPNs (Virtual Private Networks) to extend a private network across the public Internet. The IP-IP tunneling process involves adding an additional header to the original IP packet, which contains the destination address of the tunnel endpoint.
The additional header added by IP-IP tunneling is 20 bytes long. This header is known as the IP-in-IP header or the encapsulating header. It contains the following fields:
Version (4 bits): This field specifies the version of the IP protocol being used. For IP-IP tunneling, this field will be set to 4.
Internet Header Length (4 bits): This field specifies the length of the IP-in-IP header in 32-bit words. For IP-IP tunneling, this field will be set to 5.
Type of Service (8 bits): This field specifies the type of service for the encapsulated packet.
Total Length (16 bits): This field specifies the total length of the IP-in-IP packet, including both the encapsulating header and the original packet.
Identification (16 bits): This field is used to identify the IP-in-IP packet.
Flags (3 bits): This field contains various flags used to control the fragmentation and reassembly of the IP-in-IP packet.
Fragment Offset (13 bits): This field specifies the offset of the data in the IP-in-IP packet, relative to the start of the original packet.
Time to Live (8 bits): This field specifies the maximum number of hops that the IP-in-IP packet can take before being discarded.
Protocol (8 bits): This field specifies the protocol type of the encapsulated packet.
Header Checksum (16 bits): This field is used to verify the integrity of the IP-in-IP header.
Source Address (32 bits): This field contains the source IP address of the IP-in-IP packet.
Destination Address (32 bits): This field contains the destination IP address of the IP-in-IP packet, which is the address of the tunnel endpoint.
Options (variable): This field contains any optional information, such as security parameters or routing information.
In addition to the 20-byte encapsulating header, IP-IP tunneling may also add additional bytes to the original packet, depending on the specific implementation and configuration. For example, the tunneling process may add additional headers or padding to ensure that the encapsulated packet meets certain size requirements.
Therefore, the correct answer to the question is A. 20 bytes.